Method and apparatus for providing posterior or anterior trans-sacral access to spinal vertebrae

ABSTRACT

Methods and apparatus for providing percutaneous access to vertebrae in alignment with a visualized, trans-sacral axial instrumentation/fusion (TASIF) line in a minimally invasive, low trauma, manner are disclosed. A number of related TASIF methods and surgical tool sets are provided by the present invention that are employed to form a percutaneous pathway from an anterior or posterior skin incision to a respective anterior or posterior target point of a sacral surface. The percutaneous pathway is generally axially aligned with an anterior or posterior axial instrumentation/fusion line extending from the respective anterior or posterior target point through at least one sacral vertebral body and one or more lumbar vertebral bodies in the cephalad direction. The provision of the percutaneous pathway described herein allows for the formation of the anterior or posterior TASIF bore(s) and/or the introduction of spinal implants and instruments.

This application is a continuation of U.S. patent application Ser. No.09/640,222, filed Aug. 16, 2002 now U.S. Pat. No. 6,575,979, whichclaims the benefits of from Provisional Patent Application No.60/182,748, filed Feb. 16, 2000 entitled METHOD AND APPARATUS FORTRANS-SACRAL SPINAL FUSION.

FIELD OF THE INVENTION

The present invention relates generally to methods and apparatus forproviding percutaneous access to the human sacral and lumbar vertebraein alignment with a visualized, trans-sacral axialinstrumentation/fusion (TASIF) line in a minimally invasive, low trauma,manner.

BACKGROUND OF THE INVENTION

It has been estimated that 70% of adults have had a significant episodeof back pain or chronic back pain emanating from a region of the spinalcolumn or backbone. Many people suffering chronic back pain or an injuryrequiring immediate intervention resort to surgical intervention toalleviate their pain.

The spinal column or back bone encloses the spinal cord and consists of33 vertebrae superimposed upon one another in a series which provides aflexible supporting column for the trunk and head. The vertebraecephalad (i.e., toward the head or superior) to the sacral vertebrae areseparated by fibrocartilaginous intervertebral discs and are united byarticular capsules and by ligaments. The uppermost seven vertebrae arereferred to as the cervical vertebrae, and the next lower twelvevertebrae are referred to as the thoracic, or dorsal, vertebrae. Thenext lower succeeding five vertebrae below the thoracic vertebrae arereferred to as the lumbar vertebrae and are designated L1–L5 indescending order. The next lower succeeding five vertebrae below thelumbar vertebrae are referred to as the sacral vertebrae and arenumbered S1–S5 in descending order. The final four vertebrae below thesacral vertebrae are referred to as the coccygeal vertebrae. In adults,the five sacral vertebrae fuse to form a single bone referred to as thesacrum, and the four rudimentary coccyx vertebrae fuse to form anotherbone called the coccyx or commonly the “tail bone”. The number ofvertebrae is sometimes increased by an additional vertebra in oneregion, and sometimes one may be absent in another region.

Typical lumbar, thoracic and cervical vertebrae consist of a ventral orvertebral body and a dorsal or neural arch. In the thoracic region, theventral body bears two costal pits for reception of the head of a rib oneach side. The arch which encloses the vertebral foramen is formed oftwo pedicles and two lamina. A pedicle is the bony process whichprojects backward or anteriorly from the body of a vertebra connectingwith the lamina on each side. The pedicle forms the root of thevertebral arch. The vertebral arch bears seven processes: a dorsalspinous process, two lateral transverse processes, and four articularprocesses (two superior and two inferior). A deep concavity, inferiorvertebral notch, on the inferior border of the arch provides apassageway or spinal canal for the delicate spinal cord and nerves. Thesuccessive vertebral foramina surround the spinal cord. Articulatingprocesses of the vertebrae extend posteriorly of the spinal canal.

The bodies of successive lumbar, thoracic and cervical vertebraearticulate with one another and are separated by intervertebral discsformed of fibrous cartilage enclosing a central mass, the nucleuspulposus that provides for cushioning and dampening of compressiveforces to the spinal column. The intervertebral discs are anterior tothe vertebral canal. The inferior articular processes articulate withthe superior articular processes of the next succeeding vertebra in thecaudal (i.e., toward the feet or inferior) direction. Several ligaments(supraspinous, interspinous, anterior and posterior longitudinal, andthe ligamenta flava) hold the vertebrae in position yet permit a limiteddegree of movement.

The relatively large vertebral bodies located in the anterior portion ofthe spine and the intervertebral discs provide the majority of theweight bearing support of the vertebral column. Each vertebral body hasrelatively strong bone comprising the outside surface of the body andweak bone comprising the center of the vertebral body.

Various types of spinal column disorders are known and include scoliosis(abnormal lateral curvature of the spine), kyphosis (abnormal forwardcurvature of the spine, usually in the thoracic spine), excess lordosis(abnormal backward curvature of the spine, usually the lumbar spine),spondylolisthesis (forward displacement of one vertebra over another,usually in the lumbar or cervical spine) and other disorders, such asruptured or slipped discs, generative disc disease, fractured vertebra,and the like. Patients who suffer from such condition usually experienceextreme and debilitating pain and often neurologic deficit in nervefunction.

Approximately 95% of spinal surgery involves the lower lumbar vertebratedesignated as the fourth lumbar vertebra (“L4”), the fifth lumbarvertebra (“L5”), and the first sacral vertebra (“S1”). Persistent lowback pain is attributed primarily to degeneration of the disc connectingL5 and S1. There are two possible mechanisms whereby intervertebral disclesions can instigate and propagate low back pain. The first theoryproposes that the intervertebral disc itself produces pain throughtrauma or degeneration and becomes the primary source of low back pain.Proponents of this theory advocate removal of the painful disc torelieve the low back pain.

Two extensive procedures are available to remove the disc and fuse theadjacent vertebrae together. One method is to replace the disc with boneplugs by going through the spinal canal on either side of the centralnerve bundle. This method requires extensive stripping of the paraspinalmusculature. More importantly, there are extensive surgicalmanipulations within the spinal canal itself. Although the initialproponents of this approach report 90% excellent to good results,subsequent studies have been unable to obtain acceptable outcomes andrecommend adding internal fixation to improve fusion rates.

The second procedure is the anterior lumbar fusion which avoids themorbidity posterior muscle stripping by approaching the spine throughthe abdomen. Surgeons experienced with this technique also report goodto excellent patient results in 90% of cases performed. However, whengenerally used by practicing surgeons, the procedure was found to have ahigh failure rate of fusion. Attempts to increase the fusion rate byperforming a posterior stabilization procedure have been successful, butthe second incision increases the morbidity and decreases the advantagesof the technique. Thus, the present surgical techniques available toremove and fuse painful lumbar discs are extensive operative procedureswith potentially significant complications.

The other proposed mechanism for the intervertebral disc to cause lowback pain concerns its affect on associated supportive tissues. Thetheory states that disc narrowing leads to stress on all of theintervertebral structures. These include the vertebral bodies,ligamentous supports, and facet joints. Surgeries designed to fuse andstabilize the intervertebral segment can be performed through theposterior approach. This is the original surgical procedure which wasused to treat low back pain, and it also entails extensive muscularstripping and bone preparation.

There is no single procedure which is universally accepted to surgicallymanage low back pain patients. Although damaged discs and vertebralbodies can be identified with sophisticated diagnostic imaging, thesurgical procedures are so extensive that clinical outcomes are notconsistently satisfactory. Furthermore, patients undergoing presentlyavailable fusion surgery experience uncomfortable, prolongedconvalescence.

A number of devices and techniques involving implantation of spinalimplants to reinforce or replace removed discs and/or anterior portionsof vertebral bodies and which mechanically immobilize areas of the spineassisting in the eventual fusion of the treated adjacent vertebrae havealso been employed or proposed over the years In order to overcome thedisadvantages of purely surgical techniques. Such techniques have beenused effectively to treat the above described conditions and to relievepain suffered by the patient. However, there are still disadvantages tothe present fixation implants and surgical implantation techniques. Thehistorical development of such implants is set forth in U.S. Pat. Nos.5,505,732, 5,514,180, and 5,888,223, for example, all incorporatedherein by reference.

One technique for spinal fixation includes the immobilization of thespine by the use of spine rods of many different configurations that rungenerally parallel to the spine. Typically, the posterior surface of thespine is isolated and bone screws are first fastened to the pedicles ofthe appropriate vertebrae or to the sacrum and act as anchor points forthe spine rods. The bone screws are generally placed two per vertebra,one at each pedicle on either side of the spinous process. Clampassemblies join the spine rods to the screws. The spine rods aregenerally bent to achieve the desired curvature of the spinal column.Wires may also be employed to stabilize rods to vertebrae. Thesetechniques are described further in U.S. Pat. No. 5,415,661, forexample, incorporated herein by reference.

These types of rod systems can be effective, but require a posteriorapproach and implanting screws into or clamps to each vertebra over thearea to be treated. To stabilize the implanted system sufficiently, onevertebra above and one vertebra below the area to be treated are oftenused for implanting pedicle screws. Since the pedicles of vertebraeabove the second lumbar vertebra (L2) are very small, only small bonescrews can be used which sometimes do not give the needed support tostabilize the spine. These rods and screws and clamps or wires aresurgically fixed to the spine from a posterior approach, and theprocedure is difficult. A large bending moment is applied to such rodassemblies, and because the rods are located outside the spinal column,they depend on the holding power of the associated components which canpull out of or away from the vertebral bone.

In a variation of this technique disclosed in U.S. Pat. Nos. 4,553,273and 4,636,217 (both described in U.S. Pat. No. 5,735,899 incorporatedherein by reference, two of three vertebrae are joined by surgicallyobtaining access to the interior of the upper and lower vertebral bodiesthrough excision of the middle vertebral body. In the '899 patent, theseapproaches are referred to as “intraosseous” approaches, although theyare more properly referred to as “interosseous” approaches by virtue ofthe removal of the middle vertebral body. The removal is necessary toenable a lateral insertion of the implant into the space it occupied sothat the opposite ends of the implant can be driven upward and downwardinto the upper and lower vertebral bodies. These approaches arecriticized as failing to provide adequate medial-lateral and rotationalsupport in the '899 patent. In the '889 patent, an anterior approach ismade, slots are created in the upper and lower vertebrae, and rod endsare fitted into the slots and attached to the remaining vertebral bodiesof the upper and lower vertebrae by laterally extending screws.

A wide variety of anterior, extraosseous fixation implants, primarilyanterior plate systems, have also been proposed or surgically used. Onetype of anterior plate system involves a titanium plate with unicorticaltitanium bone screws that lock to the plate and are placed over theanterior surface of a vertebral body. Another type of anterior platesystem involves the use of bicortical screws that do not lock to theplate. The bone screws have to be long enough to bite into both sides ofthe vertebral body to gain enough strength to obtain the neededstability. These devices are difficult to place due to the length of thescrews, and damage occurs when the screws are placed improperly.

A number of disc shaped replacements or artificial disc implants andmethods of insertion have been proposed as disclosed, for example, inU.S. Pat. Nos. 5,514,180 and 5,888,223, for example. A further type ofdisc reinforcement or augmentation implant that has been clinicallyemployed for spinal fusion comprises a hollow cylindrical titanium cagethat is externally threaded and is screwed laterally into place in abore formed in the disc between two adjacent vertebrae. Bone grafts fromcadavers or the pelvis or substances that promote bone growth are thenpacked into the hollow center of the cage to encourage bone growththrough the cage pores to achieve fusion of the two adjacent vertebrae.Two such cage implants and the surgical tools employed to place them aredisclosed in U.S. Pat. Nos. 5,505,732 and 5,700,291, for example. Thecage implants and the associated surgical tools and approaches requireprecise drilling of a relatively large hole for each such cage laterallybetween two adjacent vertebral bodies and then threading a cage intoeach prepared hole. The large hole or holes can compromise the integrityof the vertebral bodies, and if drilled too posteriorly, can injure thespinal cord. The end plates of the vertebral bodies, which comprise veryhard bone and help to give the vertebral bodies needed strength, areusually destroyed during the drilling. The cylindrical cage or cages arenow harder than the remaining bone of the vertebral bodies, and thevertebral bodies tend to collapse or “telescope,” together. Thetelescoping causes the length of the vertebral column to shorten and cancause damage to the spinal cord and nerves that pass between the twoadjacent vertebrae.

Methods and apparatus for accessing the discs and vertebrae by lateralsurgical approaches are described in U.S. Pat. No. 5,976,146. Theintervening muscle groups or other tissues are spread apart by a cavityforming and securing tool set disclosed in the '146 patent to enableendoscope aided, lateral access to damaged vertebrae and discs and toperform corrective surgical procedures.

R. Johnsson et al. report the results of the use of biodegradable rodsto augment posterolateral fusion of L5–S1 or L4–S1 in “Posterolaterallumbar fusion using facet joint fixation with biodegradeable rods: apilot study” Eur Spine J 6:14–48′ (1997). In this surgical technique,the posterolateral surfaces of the lumbrosacral spine were exposed, andtwo canals were bored through facets of the vertebrae to be fused. A rodformed of self-reinforced polyglycolic acid composite material wasinserted through each canal, and fixed by absorption of body fluids andexpansion therein. While successful fusion of L5–S1 was reported in anumber of cases, fusion of L4–S1 was unsuccessful or inadequate, andlateral surgical exposure and stripping of the vertebrae facets wasstill necessary.

A compilation of the above described surgical techniques and spinalimplants and others that have been used clinically is set forth incertain chapters of the book entitled Lumbosacral and SpinopelvicFixation, edited by Joseph Y. Margolies et al. (Lippincott-RavenPublishers, Philadelphia, 1996). Attention is directed particularly toChapters 1, 2, 16, 18, 38, 42 and 44. In “Lumbopelvic Fusion” (Chapter38 by Prof. Rene P. Louis, MD) techniques for repairing aspondylolisthesis, that is a severe displacement of L5 with respect toS1 and the intervening disc, are described and depicted. An anteriorlateral exposure of L5 and S1 is made, a discectomy is performed, andthe orientation of L5 to S1 is mechanically corrected using a reductiontool, if the displacement is severe. A fibula graft or metal Judet screwis inserted as a dowel through a bore formed extending caudally throughL5 and into S1. Further spacer implants are placed in the space occupiedby the extracted disc between L5 and S1. External bridge plates or rodsare also optionally installed.

The posterolateral or anterior lateral approach is necessitated tocorrect the severe spondylolisthesis displacement using the reductiontool and results in tissue injury. Because of this approach and need,the caudal bore and inserted the Judet screw can only traverse L5 andS1.

The above-described spinal implant approaches involve highly invasivesurgery that laterally exposes the anterior or posterior portions of thevertebrae to be supported or fused. Extensive muscular stripping andbone preparation can be necessary. As a result, the spinal column can befurther weakened and/or result in surgery induced pain syndromes. Thus,presently used surgical fixation and fusion techniques involving thelower lumbar vertebrae suffer from numerous disadvantages. It ispreferable to avoid the lateral exposure to correct less severespondylolisthesis and other spinal injuries or defects affecting thelumbar and sacral vertebrae and discs.

A wide variety of orthopedic implants have also been proposed orclinically employed to stabilize broken bones or secure artificial hip,knee and finger joints. Frequently, rods or joint supports are placedlongitudinally within longitudinal bores made in elongated bones, e.g.,the femur. A surgical method is disclosed in U.S. Pat. No. 5,514,137 forstabilizing a broken femur or other long bones using an elongated rodand resorbable cement. To accomplish a placement of a rod into anysingle bone, an end of a bone is exposed and a channel is drilled fromthe exposed end to the other end. Thereafter, a hollow rod is inserted,and resorbable cement is injected through the hollow rod, so as toprovide fixation between the distal end of the rod and the cancelloustissue that surrounds the rod. A cement introducer device can also beused for the injection of cement. A brief reference is made in the '137patent to the possibility of placing rods in or adjacent to the spine inthe same manner, but no particular approach or devices are described.

The present invention has at least one objective of providing apractical and advantageous system, method and tools for accessing thespinal vertebrae to repair or augment damaged vertebrae and discs or toinsert spinal implants in various manners that overcome the abovedescribed disadvantages of posterior and anterior lateral approachesthereto and minimize surgical trauma to the patient.

SUMMARY OF THE INVENTION

The methods and surgical instrumentation of the present inventionprovide posterior and anterior trans-sacral access to a series ofadjacent vertebrae located within a human lumbar and sacral spine havingan anterior aspect, a posterior aspect and an axial aspect, thevertebrae separated by intact or damaged spinal discs. A number ofrelated trans-sacral axial spinal instrumentation/fusion (TASIF) methodsand surgical tool sets are provided by various alternative embodimentsof the present invention. Certain of the tools are selectively employedto form a percutaneous (i.e., through the skin) pathway from an anterioror posterior skin incision to a respective anterior or posteriorposition, e.g., a target point of a sacral surface or the cephalad endof a pilot hole bored through the sacrum and one or more lumbarvertebrae. The percutaneous pathway is generally axially aligned with ananterior axial instrumentation/fusion line (AAIFL) or a posterior axialinstrumentation/fusion line (PAIFL) extending from the respectiveanterior or posterior target point through at least one sacral vertebralbody and one or more lumbar vertebral body in the cephalad direction andvisualized by radiographic or fluoroscopic equipment. The AAIFL andPAIFL follow the curvature of the vertebral bodies, although the AAIFLcan be straight or relatively straight, depending on the number ofvertebrae that the AAIFL is extended through.

The anterior or posterior percutaneous pathway so formed enablesintroduction of further tools and instruments for forming an anterior orposterior percutaneous tract extending from the skin incision to therespective anterior or posterior target point of the sacral surface or,in some embodiments, the cephalad end of a pilot hole over which orthrough which further instruments are introduced. The “anterior,presacral, percutaneous tract” disclosed herein extends through the“presacral space” anterior to the sacrum.

The anterior or posterior percutaneous tract is preferably used to boreone or more respective anterior or posterior TASIF bore in the cephaladdirection through one or more lumbar vertebral bodies and interveningdiscs, if present. A single anterior or posterior TASIF bore ispreferably aligned axially with the respective visualized AAIFL orPAIFL, and plural anterior or posterior TASIF bores are preferablyaligned in parallel with the respective visualized AAIFL or PAIFL.Introduction of spinal implants and instruments for performingdiscectomies and/or disc and/or vertebral body augmentation is enabledby the provision of the percutaneous pathway in accordance with thepresent invention and formation of the anterior or posterior TASIFbore(s).

The posterior percutaneous tract preferably extends from a posteriorskin incision into the posterior sacrum to a posterior target pointexposed by a laminectomy. This posterior percutaneous tract has a tractaxis aligned with the visualized PAIFL to provide working space,exposure of the sacrum, and alignment of the boring tool with thevisualized PAIFL. The posterior percutaneous tract can take the form ofa lumen of a tract sheath introduced through the percutaneous pathway ora guidewire whereby the guidewire provides a percutaneous tract for overthe wire passage extending from the skin incision to the posteriortarget point and aligned with the visualized PAIFL. Either or both ofthe tract sheath or guidewire can comprise distal fixation mechanismsthat enable fixation to the sacral vertebral surface at the posteriortarget point for through the sheath or over the wire introduction ofboring tools or other instruments. Prior to boring the posterior TASIFbore(s), a pilot hole for each such posterior TASIF bore is optionallybored along or parallel with the visualized PAIFL, and the guidewiredistal end is affixed to vertebral bone at the cephalad end of the pilothole to provide the percutaneous tract for guiding a drill or otherinstrument to form the posterior TASIF bore or conduct discectomies ordisc or vertebral bone augmentation.

Certain of the surgical tools take the form of elongated solid bodymembers extending from proximal to distal ends thereof. Such solid bodymembers may be used in combination with or sequentially with elongatedhollow body members. Certain of these solid body and hollow body memberscan have distal fixation mechanisms for attachment to bone and/or can beangles to be aligned with and bear against sacral bone.

The anterior percutaneous pathway is preferably accomplished employingan elongated guide member that is introduced through the skin incisionand advanced against the anterior sacrum through the presacral spaceuntil the guide member distal end is located at the anterior targetpoint. The posterior viscera are pushed aside as the guide member isadvanced through presacral space and axially aligned with the AAIFL atthe anterior target point of the anterior sacral surface.

The guide member may take a variety of forms including a blunt tip rodor a guide assembly of an inner occluder and an outer tubular memberfitted together having a tubular member lumen receiving the occluder.The occluder may take the form of a solid body member, e.g., anobdurator, a stylet, a guidewire or the like, and the tubular member maytake the form of a needle, a trocar, a catheter or the like. Either orboth of the inner occluder and outer tubular member may comprise distalfixation mechanisms that enable fixation to the sacral vertebral surfaceat the anterior target point and/or at the cephalad end of a pilot holefor each such anterior TASIF bore optionally bored along or parallelwith the visualized AAIFL. The occluder can be employed to blunt the tipof the outer tubular member during introduction to the anterior targetpoint, if the outer tubular member comprises a distal tip fixationmechanism that would otherwise prematurely engage the sacral bone. Orthe occluder can have a distal tip fixation mechanism and be retractedwithin the outer tubular member to prevent its premature attachment tosacral bone during introduction to the anterior target point.

In its simplest forms, the anterior, presacral, percutaneous tract cantake the form of the lumen of the outer tubular member upon removal ofthe occluder. The anterior percutaneous pathway can be expanded to formthe anterior, presacral, percutaneous tract through the patient'santerior presacral space having a tract axis aligned with the visualizedAAIFL to provide working space and exposure of the sacrum. In oneembodiment, a guidewire having a distal fixation mechanism (which maycomprise the occluder) provides the anterior, presacral, percutaneoustract for over-the-wire passage extending from the skin incision to thetarget point and aligned with the visualized AAIFL. In furtherembodiments, the lumen of a further tract sheath introduced through thepercutaneous pathway, e.g., over the guidewire or after removal of theguidewire, provides a percutaneous tract for over the wire passageextending from the skin incision to the target point and aligned withthe visualized AAIFL. The further tract sheath preferably has a distaltract sheath fixation mechanism and configuration that enables alignmentand attachment to the anterior sacral bone at the anterior target pointto maintain the tract sheath lumen aligned axially with a the visualizedAAIFL.

The tissue surrounding the skin incision and the anterior, presacral,percutaneous pathway through the presacral space may optionally bedilated to form an enlarged diameter presacral, percutaneous tractsurrounding a guidewire or tubular member and/or to accommodate theinsertion of a tract sheath over the guidewire. Dilation can beaccomplished manually or by use of one or more dilator or dilatationballoon catheter or any tubular device fitted over a previously extendedtubular member or guidewire.

Additionally, a pilot hole can be bored in axial alignment or parallelwith the visualized AAIFL by a boring tool introduced through the outertubular member lumen for each such anterior TASIF bore bored along orparallel with the visualized AAIFL. The guidewire distal end fixationmechanism is then affixed to vertebral bone at the cephalad end of thepilot hole to provide the percutaneous tract for guiding a drill orother instrument to form the anterior TASIF bore or conduct discectomiesor disc or vertebral bone augmentation.

In particular embodiments of the present invention, in the anteriorTASIF approach, the junction of S1 and S2 is located through apresacral, percutaneous tract posterior to the rectum and extending froma skin incision adjacent the coccyx. A relatively straight anteriorTASIF axial bore into at least L5 can be formed in the vertebral columnaccessed via the anterior, presacral, percutaneous tract to receive aTASIF implant or interventional tools inserted through the anterior,presacral, percutaneous tract. However, the anterior TASIF axial borecan also be curved to follow the curvature of the vertebrae L4, L3, etseq. in the cephalad direction following a visualized, curved, AAIFLextending therethrough.

a preferred posterior TASIF approach, the posterior sacrum is exposed, alaminectomy is performed at S2, and the posterior percutaneous tract isformed using one of the above-summarized procedures and percutaneoustract tool sets. A curved axial bore is then made upwardly through S2,S1 and into at least L5 and optionally extended and curved to follow thecurvature of the vertebrae L4, L3, et seq. in the cephalad direction. Acurved TASIF implant or rod can be inserted into the TASIF axial bore tobridge the vertebrae and the intervening discs, if present.

Thus, the various embodiments of the present invention provide access toanterior and posterior target points of the anterior or posterior sacrumpreparatory to forming anterior or posterior TASIF bores that extend inthe cephalad direction and can be employed to introduce instruments fortreatment of vertebral bodies, intervertebral discs and introduction ofaxially aligned spinal implants as described in further detail in theabove-referenced provisional application No. 60/182,748. In either theposterior or anterior approach, multiple bores may be made side-by-sideto receive multiple spinal implants.

The access procedures for forming the anterior or posterior percutaneoustract and the subsequently conducted surgical repair and/or implantationprocedures are minimally invasive and requires a short, if any,post-implantation hospitalization and recovery period and reduceddiscomfort to the patient. The access procedures avoid the musclestripping required to access the vertebrae and/or discs or removal ofstrong anterior vertebral body bone and intervening discs attendant tothe conventional lateral surgical approaches described above

The anterior and posterior TASIF approaches also allow disc surgery ordisc augmentation through the TASIF bore or pilot hole of all discstraversed by the TASIF axial bore or pilot hole in a minimally invasivemanner. Moreover, these approaches can be employed a minimally invasivemanner to perform vertebroblasty of the vertebrae traversed by the TASIFaxial bore or pilot hole to augment the vertebral bone in cases ofcompression fracture of the vertebral bone. Vertebroblasty is procedurefor augmentation of collapsed vertebral bodies by pumped in materials,e.g., bone cement. In the past, it has been accomplished through alateral approach of a needle into a single vertebral body and pumpingthe cement through the needle lumen. The present invention allows largerdiameter access to multiple vertebral bodies through the axial approach.

The present invention further enables use of a number of differing typesof TASIF implants or rods that can be inserted into the TASIF axial boreor bores. Such implantable vertebral prostheses align, strengthen, andfuse the adjacent vertebrae particularly in the lumbar region of thespinal column. The elongated, axially extending TASIF implants or rodsimplanted using the percutaneous tracts formed in accordance with thepresent invention reinforce the relatively strong anterior vertebralbodies and should prevent potentially damaging telescoping of adjacentvertebrae.

The TASIF spinal implants or rods can be implanted in accordance withthe present invention in a less traumatic manner than conventionallateral exposure and placement of conventional vertebral prostheses, andthe need to implant screws or extend wires laterally through thevertebral bodies and a rod or rods is eliminated. Unlike conventionalspinal rods, the TASIF implants or rods that can be implanted inherentlypossess a low profile and would usually not be felt by the patient afterhealing.

Moreover, it is contemplated that the anterior or posterior TASIF pilothole or axial bore may also be used to receive pain relief stimulationelectrodes coupled through leads to implantable pulse generators forproviding electrical stimulation of the bone and adjoining nerves forpain relief and/or to stimulate bone growth. Other therapeutic spinalimplants can be implanted therein to elute drugs or analgesics or emitradiation for treatment of various diseases or pain syndromes.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other advantages and features of the present invention will bemore readily understood from the following detailed description of thepreferred embodiments thereof, when considered in conjunction with thedrawings, in which like reference numerals indicate identical structuresthroughout the several views, and wherein:

FIGS. 1–3 are lateral, posterior and anterior views of the lumbar andsacral portion of the spinal column depicting the visualized PAIFL andAAIFL extending cephalad and axially from the posterior laminectomy siteand the anterior target point, respectively;

FIG. 4 is a sagittal caudal view of lumbar vertebrae depicting a TASIFspinal implant or rod within a TASIF axial bore formed following thevisualized PAIFL or AAIFL of FIGS. 1–3;

FIG. 5 is a sagittal caudal view of lumbar vertebrae depicting aplurality, e.g., 2, TASIF spinal implants or rods within a likeplurality of TASIF axial bores formed in parallel with the visualizedPAIFL or AAIFL of FIGS. 1–3;

FIG. 6 is a simplified flow chart showing the principal surgicalpreparation steps of percutaneously accessing a posterior or anteriortarget point of the sacrum and forming a percutaneous tract followingthe visualized PAIFL or AAIFL of FIGS. 1–3 as well as subsequent stepsof forming the TASIF bore(s) for treatment of accessed vertebral bodiesand intervening discs and/or implantation of spinal implants therein;

FIGS. 7–9 depict the principal surgical preparation and implantationsteps of forming a posterior percutaneous tract enabling access forforming one or more posterior TASIF axial bore following the visualizedPAIFL of FIGS. 1 and 2;

FIGS. 10 and 11 are views of embodiments of a motor driven, canted tip,drill for drilling a posterior pilot hole following the visualized PAIFLof FIGS. 1 and 2;

FIG. 12 is a flow chart expanding upon step S100 of FIG. 6 showing theprincipal surgical preparation steps of forming various types ofanterior, presacral, percutaneous tracts axially aligned with thevisualized AAIFL of FIGS. 1 and 3 through presacral space posterior tothe patient's rectum;

FIGS. 13–21 illustrate various tools employed in various combinationsand sequence for forming the various types of anterior, presacral,percutaneous tracts used in performing the anterior tract forming stepsset forth in FIG. 12;

FIGS. 22–26 illustrate the use of certain tools of FIGS. 13–17 followingsteps of FIG. 12 to form anterior, presacral, percutaneous tractsthrough the presacral space that are axially aligned with the visualizedAAIFL of FIGS. 1 and 3 either surrounding inner occluder or an outertubular member of a guide assembly;

FIG. 27 illustrates the use of one form of dilator(s) shown in FIGS.20–21 to dilate the presacral space and expand the anterior, presacral,percutaneous tract in accordance with optional steps S116 and S118 ofFIG. 12;

FIGS. 28–29 illustrate insertion of an enlarged tubular anterior tractsheath illustrated in FIG. 13 having an angled distal end through thedilated presacral tissue to form an enlarged anterior, presacral,percutaneous tract comprising the anterior tract sheath lumen inaccordance with optional steps S120 and S122 of FIG. 12;

FIGS. 30–31 illustrate insertion of an enlarged tubular anterior tractsheath having a distal fixation mechanism through the dilated presacraltissue to form an enlarged anterior, presacral, percutaneous tractcomprising the anterior tract sheath lumen in accordance with optionalsteps S120 and S122 of FIG. 12;

FIG. 32 is a flow chart showing particular steps of attaching aguidewire to the anterior target point to form an anterior, presacral,percutaneous tract maintained in axial alignment with the AAIFL;

FIG. 33 is a flow chart showing alternative particular steps ofattaching a guidewire to the anterior target point to form an anterior,presacral, percutaneous tract maintained in axial alignment with theAAIFL;

FIG. 34 is a flow chart showing steps of forming a pilot hole trackingthe AAIFL and attaching a guidewire to the cephalad end of the pilothole to form an anterior, presacral, percutaneous tract about theguidewire maintained in axial alignment with the AAIFL;

FIGS. 35–39 illustrate certain of the steps of FIG. 34;

FIG. 40 is a flow chart showing steps of dilating the presacral tissuearound the affixed guidewire of FIG. 39 and the insertion of an enlargedtubular anterior tract sheath through the dilated presacral space toform the anterior, presacral, percutaneous tract comprising the anteriortract sheath lumen;

FIGS. 41–43 illustrate certain of the steps of FIG. 40; and

FIG. 44 is a view of one form of pilot hole or TASIF axial bore holeboring tool for forming a pilot hole or TASIF axial bore that isstraight or curved in whole or in part;

FIG. 45 is a view of another form of pilot hole or TASIF axial bore holeboring tool for forming a pilot hole or TASIF axial bore that isstraight or curved in whole or in part; and

FIG. 46 illustrates the step of forming an anterior TASIF axial borehole using an enlarged diameter drill bit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The preferred embodiments of the invention involve methods and apparatusincluding surgical tool sets for forming anterior and posteriorpercutaneous tracts for accessing anterior and posterior target pointsof the sacrum in alignment with the visualized AAIFL and PAIFL. Incertain embodiments, pilot holes may be bored in the cephalad directionthrough one or more sacral and lumbar vertebral bodies in alignment withthe visualized AAIFL and PAIFL and used as part of the anterior andposterior percutaneous tracts.

As noted above and shown in the above-referenced provisional applicationNo. 60/182,748, the pilot holes of the anterior and posteriorpercutaneous tracts can be used to introduce instruments to inspectand/or perform therapies upon the vertebral bodies or intervening discs.The posterior or anterior pilot hole may optionally be used as theposterior or anterior TASIF axial bore, respectively, axially alignedwith the PAIFL or AAIFL, respectively, to receive spinal implants ofvarious types.

The access to the anterior and posterior target points or pilot holesoffered by the anterior and posterior percutaneous tracts can be used toform larger diameter or particularly shaped TASIF bores, which are alsoreferred to as TASF bores in the above-reference parent provisionalapplication No. 60/182,748. The enlarged diameter or otherwise shapedTASIF bores can be used to introduce instruments to inspect and/orperform therapies upon the vertebral bodies or intervening discs and/orinsert spinal implants as set forth in the above-referenced parentprovisional application No. 60/182,748 and further described herein.

The following description of FIGS. 1–6 is taken from theabove-referenced parent provisional application No. 60/182,748. Theacronyms TASF, AAFL, and PAFL are changed to TASIF, AAIFL and PAIFL inthis application to explicitly acknowledge that instruments can beintroduced for inspection or treatments in addition to the fusion andfixation provided by spinal implants that may be inserted into the axialbores or pilot holes.

FIGS. 1–3 schematically illustrate the anterior and posterior TASIFsurgical approaches in relation to the lumbar region of the spinalcolumn, and FIGS. 4–5 illustrate the location of the TASIF implant orpair of TASIF implants within a corresponding TASIF axial bore 22, 152or pair of TASIF axial bores 22 ₁, 152 ₁, and 22 ₂, 152 ₂. PreferredTASIF surgical approaches for providing anterior and posteriortrans-sacral access depicted in FIGS. 1–3 and preparing the TASIF axialbores 22, 152 and 22 ₁, 152 ₁/22 ₂, 152 ₂ shown in FIGS. 4 and 5 areillustrated in further drawings. Preferred trans-sacral surgical accessand TASIF pilot hole preparation tools are depicted in further drawings.Various representative embodiments of TASIF implants or rods usable inthe TASIF axial bores 22, 152 and 22 ₁, 152 ₁/22 ₂, 152 ₂ of FIGS. 4 and5 are depicted in the above-referenced parent provisional applicationNo. 60/182,748. Two TASIF axial bores and spinal implants or rods areshown in FIG. 5 to illustrate that a plurality, that is two or more, ofthe same may be formed and/or employed in side by side relation parallelwith the AAIFL or PAIFL.

The lower regions of the spinal column comprising the coccyx, fusedsacral vertebrae S1–S5 forming the sacrum, and the lumbar vertebraeL1–L5 described above are depicted in a lateral view in FIG. 1. Theseries of adjacent vertebrae located within the human lumbar and sacralspine have an anterior aspect, a posterior aspect and an axial aspect,and the lumbar vertebrae are separated by intact or damaged spinal discslabeled D1–D5 in FIG. 1. FIGS. 2 and 3 depict the posterior and anteriorview of the sacrum and coccyx.

In accordance with the present invention, the method and apparatus forfusing at least L4 and L5 and optionally performing a discectomy of D5and/or D4 involves accessing an anterior sacral position, e.g. ananterior target point at the junction of S1 and S2 depicted in FIGS. 1and 3, or a posterior sacral position, e.g. a posterior laminectomy siteof S2 depicted in FIGS. 1 and 2. One (or more) visualized, imaginary,axial instrumentation/fusion line extends cephalad and axially in theaxial aspect through the series of adjacent vertebral bodies to befused, L4 and L5 in this illustrated example. The visualized AAIFLthrough L4, D4, L5 and D5 extends relatively straight from the anteriortarget point along S1 depicted in FIGS. 1 and 3, but may be curved as tofollow the curvature of the spinal column in the cephalad direction. Thevisualized PAIFL extends in the cephalad direction with more pronouncedcurvature from the posterior laminectomy site of S2 depicted in FIGS. 1and 2.

It should be noted that the formation of the anterior tract 26 throughpresacral space under visualization described above is clinicallyfeasible as evidenced by clinical techniques described by J. J.Trambert, MD, in “Percutaneous Interventions in the Presacral Space:CT-guided Precoccygeal Approach—Early Experience (Radiology 1999;213:901–904).

FIG. 6 depicts, in general terms, the surgical steps of accessing theanterior or posterior sacral positions illustrated in FIGS. 1–3 (S100)forming posterior and anterior TASIF axial bores (S200), optionallyinspecting the discs and vertebral bodies, performing disc removal, discaugmentation, and vertebral bone reinforcement (S300), and implantingposterior and anterior spinal implants and rods (S400) in a simplifiedmanner. In step S100, access to the anterior or posterior sacralposition, that is the anterior target point of FIG. 3 or the posteriorlaminectomy site of FIG. 2 is obtained, and the anterior or posteriorsacral position is penetrated to provide a starting point for each axialbore that is to be created. Then, an axial bore is bored from each pointof penetration extending along either the PAIFL or AAIFL cephalad andaxially through the vertebral bodies of the series of adjacent vertebraeand any intervening spinal discs (S200). The axial bore may be visuallyinspected using an endoscope to determine if the procedures of step S300should be performed. Discoscopy or discectomy or disc augmentation of anintervening disc or discs or vertebroblasty may be performed through theaxial bore (S300). Finally, an elongated TASIF spinal implant or rod isinserted into each axial bore to extend cephalad and axially through thevertebral bodies of the series of adjacent vertebrae and any interveningspinal discs (S400). Other types of spinal implants for deliveringtherapies or alleviating pain as described above may be implantedsubstitution for step S400.

It should be noted that performing step S100 in the anterior and/orposterior TASIF procedures may involve drilling a pilot hole, smaller indiameter than the TASIF axial bore, that tracks the AAIFL and/or PAIFLin order to complete the formation of the anterior and/or posteriorpercutaneous tracts. Step S300 may optionally be completed through theAAIFL/PAIFL pilot hole following step S100, rather than following theenlargement of the pilot hole to form the TASIF axial bore in step S200.

Posterior Approach

Step S100 of FIG. 6 is performed in the posterior TASIF procedure asfollows. It is expected that the patient 10, depicted in FIG. 7 in apartial side cross-section view, will lie prone on a surgical tablehaving reverse lordosis support. An imaging system (not shown), whichmay be an MRI scanner, a CT scanner or preferably a bi-plane fluoroscopymachine, is employed first to show the spinal structure and adjacenttissues, vessels and nerves for visualizing the PAIFL through thevisible landmarks of the sacrum and lumbar vertebrae. Then, the imagingsystem is employed during the surgical creation of the posterior TASIFaxial bore to ensure that it remains within the vertebral bodies andintervening discs following the PAIFL and does not stray anteriorly,posteriorly or laterally therefrom.

The area of the patient's skin 12 surrounding the incision site issurgically prepped, and the anus is excluded from the surgical fieldusing adhesive drapes. The actual dermal entry site may be determined bythe prone, preoperative CT scan or MRI study that maps the PAIFL. Instep S100, depicted in FIG. 7, an incision is made in the patient's skin12 over the posterior sacral surface of S2 and a posterior tract 18 isformed through the subcutaneous tissue to expose the posteriorlyextending, bony ridge of the posterior sacral surface. A smalllaminectomy 14 is performed through the posterior ridge of the sacruminferior. The thecal sac and nerve roots that are exposed by thelaminectomy are gently retracted, and the terminal portion of the spinalcanal is exposed.

The posterior sacral position or target point is exposed by thelaminectomy and through the posterior percutaneous pathway. Inaccordance with the present invention, a posterior percutaneous tract isprovided that enables the precise stabilization and positioning of pilothole boring and/or posterior TASIF axial bore forming tools for boringthe pilot hole and/or posterior TASIF axial bore.

The posterior percutaneous tract can take the form of a guidewire 80depicted in FIG. 8 that is affixed at its distal end to the sacrum atthe posterior target point. The distal fixation mechanism may comprise adistal screw-in tip 82 as shown in FIG. 8 or may take other forms, e.g.,the hook or barb 82′ depicted in FIGS. 18 and 19. A proximal, removable,guidewire handle 81 is used to rotate the guidewire 80 to screw distalscrew-in tip 82 into and out of the sacral bone, and is removed at othertimes. The guidewire 80 then provides a percutaneous tract extendingfrom the skin incision 18 to the posterior target point that is alignedwith the visualized PAIFL The guidewire formed posterior percutaneoustract provides over-the-wire guidance of a drill or boring instrumentfor boring a pilot hole or posterior TASIF axial bore passage Thecharacteristics and alternative forms that the guidewire 80 may take aredescribed further below in reference to FIG. 13. The guidewire 80 may beintroduced through the percutaneous pathway as an occluder within thelumen of an outer, stiffer, tubular member in the manner described belowin the anterior approach in reference to FIG. 25. The distal screw-intip 82 can then be advanced distally, and screwed in while the outertubular member confines the guidewire shaft. Then the outer tubularmember is removed.

The posterior percutaneous tract can also take the form of a lumen of aposterior tract sheath introduced through the posterior percutaneouspathway. Such a posterior tract sheath 30 is depicted in FIG. 9 having atract sheath lumen 32 extending from a proximal sheath end 34 to adistal sheath end 36. The distal sheath end 36 is formed with a distalsheath end fixation mechanism for anchoring the distal sheath end 36 tothe sacrum at the posterior surface of S2, for example. The depicteddistal sheath end fixation mechanism comprises a threaded tip that canbe screwed into bone, although a starting hole may have to be firstformed so that the screw threads can be advanced and the posterior tractsheath can be firmly fixed to the sacrum.

As shown in FIG. 9, the tract sheath lumen 32 provides a posteriorpercutaneous tract that is axially aligned to starting point of thevisualized PAIFL 20, and the tract sheath 30 then functions as a boringtool or drill guide to assist in keeping the boring tool or drill ontract. FIG. 10 depicts the use of the posterior tract sheath 30 with adrill 40 for drilling or boring a posterior pilot hole 38 from theposterior target point at S2 along the visualized PAIFL 20 prior toboring the posterior TASIF bore. This two step approach further involvesthe insertion of the guidewire through the pilot hole 38 and affixationof the guidewire distal fixation mechanism into the vertebral body boneat the cephalad end of the pilot hole 38 as shown in FIG. 11. Theguidewire 80 affixed to the vertebral bone at the cephalad end of thepilot hole provides the posterior percutaneous tract for guiding a drillor other instrument to form an enlarged posterior TASIF bore or forconducting discectomies or disc or vertebral bone augmentation.

Alternatively, the tract sheath 30 may provide the starting point andguide the direct drilling or boring of the posterior TASIF axial bore(s)without forming the pilot hole and employing the guidewire 80 in themanner depicted in FIG. 11.

In FIG. 10, the posterior TASIF pilot hole 38 extends through thecenters of two or more vertebral bodies L4, L5 and intervening discsanterior to and extending in parallel with the thecal sac (also shown inFIG. 4, for example). A drill bit 44 at the distal end of a directionaldrill sheath 42 of a drill 40 or 40′ (depicted in FIGS. 10 and 11) iscarefully advanced using bi-plane fluoroscopic visualization (or othervisualization) through the sheath lumen 32 operating as a drill guide.The drill drive shaft 46, 46′ within the drill sheath 42 is rotated bythe drill motor to rotate the drill bit 44, 44′ as it is advanced underfluoroscopic observation along the visualized PAIFL 20 and form thecurved posterior TASIF pilot hole 38.

Suitable exemplary directional drills 40 and 40′ are schematicallydepicted in FIGS. 44 and 45. The drill 40 of FIG. 44 comprises a drillmotor housing 50 coupled with drill sheath 42 enclosing the drill driveshaft 46. The drill motor housing 50 includes a motor 48 powered by abattery 54. The drill motor 48 is coupled to the battery 54 bymanipulation of a power switch 52 to rotate the drive shaft 46 and drillbit 44 of drill 40.

A pull wire 45 extends through a pull wire lumen 49 extending along oneside of the sheath 42 between its distal end and a tip curvature control47 on drill motor housing 50. The distal end portion of drill sheath 42is flexible, and retraction of pull wire 45 by manipulation of tipcurvature control 47 causes the distal end portion of drill sheath 42 toassume a curvature from the straight configuration as shown in phantomlines in FIG. 44. The surgeon can manipulate tip curvature control 47 tocontrol the curvature of the distal end portion of drill sheath 42 andthe TASIF axial bore 22.

The drill 40′ of FIG. 45 comprises a drill motor housing 50′ coupledwith drill sheath 42′ enclosing the drill drive shaft 46′. The drillmotor housing 50′ includes a battery 54′ and motor 48′ that is turned onby manipulation of a power switch 52′ to rotate the drive shaft 46′ anddrill bit 44′ of drill 40′. In this embodiment, the distal end portion56 of drill sheath 42 is pre-curved or canted at about 20°, for example,providing an eccentric drill bit 44′. The eccentric drill bit 44′ has aninherent tendency to “veer” in the direction of rotation of the drillbit. Rotating the drill sheath 42′ during advancement along thevisualized axial instrumentation/fusion line 20 causes it to form theTASIF pilot hole 38 that follows the curved PAIFL of FIG. 1.

Thus, the drilling of the posterior TASIF axial bore 22 may beundertaken in sequential steps of first drilling a small diameter pilothole along the PAIFL 20 using the drill 40 or 40′, inserting a guidewirethrough the pilot hole, and then enlarging the pilot hole to form thecurved posterior TASIF axial bore. The posterior TASIF axial boreforming tool set may be similar to the anterior TASIF axial bore formingsteps and tools described below. Using this technique to form theposterior TASIF axial bore 22, a small diameter drill bit and drillshaft (e.g. 3.0 mm diameter) is used to first drill a small diameterpilot hole 38 following the imaginary, visualized PAIFL 20 through S1,L5 and L4. Then, the drill bit and shaft are removed, and the guidewire80 having the threaded distal screw-in tip 82 is advanced through thepilot hole 38 and screwed into to the cephalad end of the pilot hole 38and into the L4 vertebral body. An over-the-wire bore enlarging tool isfitted over the proximal end of the guidewire and manually ormechanically rotated and advanced along it in the manner described belowwith regard to the formation of the larger diameter, e.g. a 10.0 mmdiameter, anterior TASIF axial bore. In this way, the pilot holediameter is enlarged to form the anterior TASIF axial bore, and theenlarging tool is then removed.

The longitudinal, curved, posterior TASIF axial bore(s) 22 (shown inFIGS. 4 and 5) formed in step S200 of FIG. 6 starts in the sacrum at theposterior target point or position exposed by the laminectomy andextends upwardly or cephalad through the vertebral body of S1 or S2 andthrough the cephalad vertebral bodies including L5 and L4 and theintervening discs denoted D4 and D5 in FIG. 1. Discs D4 and D5 areusually damaged or have degenerated between lumbar spine vertebrae andcause the pain experienced by patients requiring intervention and fusionof the vertebrae. An inspection of the vertebral bodies and discs alongthe sides of the TASIF axial bore 22 can be made using an elongatedendoscope inserted through the TASIF axial bore or the pilot hole 38 ifone is formed. A discectomy or disc augmentation and/or vertebroblastymay be performed pursuant to step S300 of FIG. 6 through the posteriorTASIF axial bore 22 or pilot hole 38 and laminectomy site to relieve thepatient's symptoms and aid in the fusion achieved by-the posteriorspinal implant or rod.

Anterior Approach:

Turning to the anterior TASIF approach, FIG. 12 expands upon step S100of FIG. 6 showing the principal surgical preparation steps of forming ananterior, presacral, percutaneous tract 26 axially aligned with thevisualized AAIFL of FIGS. 1 and 3 through presacral space 24 posteriorto the patient's rectum. The anterior tract forming steps of FIG. 12 areperformed using certain of the tools of an anterior tract forming toolset 60 that is shown in FIG. 13 and optionally using additional oralternative tools illustrated in FIGS. 14–21. Certain additional oralternative surgical procedure steps are set forth in FIGS. 32–34 and40. The remaining figures illustrate the surgical tools as used incertain of these steps.

Certain of the surgical tools take the form of elongated solid bodymembers extending from proximal to distal ends thereof. Elongated solidbody members in medical terminology include relatively stiff or flexibleneedles of small diameter typically used to penetrate tissue, wirestylets typically used within electrical medical leads or catheters tostraighten, stiffen, or impart a curved shape to the catheter,guidewires that are used to traverse body vessel lumens and accessremote points therein (certain hollow body guidewires have lumens for anumber of uses), and obdurators. Obdurators are typically formed as rodsprovided in various diameters with blunt distal tips that can bemanipulated to penetrate, separate or manipulate tissue without cuttingor other damage. In the vernacular of the present invention, the term“guidewire” is employed herein to embrace any such solid body member(guidewire type) that can be employed to perform the functions ofover-the-wire delivery and guidance described herein unless theexclusive use of a given one of such solid body members is explicitlystated. Such solid body members may be stiff or flexible and may includedistal fixation mechanisms.

Certain others of the surgical tools take the form of hollow body,tubular members having lumens extending from proximal to distal endsthereof. Such hollow body, tubular members can take the form of medicalcatheters, medical cannulas, medical tubes, hollow needles, trocars,sheaths, and the like. Such hollow body tubular members employed invarious embodiments of the present invention may be stiff or flexibleand may include distal fixation mechanisms.

In addition, the term “occluder” is employed herein to comprise any formof elongated tool that is inserted into a tubular member lumen and thatentirely or partly occludes the lumen of the tubular member and mayextend distally from the tubular member distal end. Any of the guidewiretypes can function as an occluder of the lumen of any of the tubularmember types.

The anterior tract tool set 60 depicted in FIG. 13 and variations andmodifications thereof shown in FIGS. 14–19 include a number of surgicaltools that can be used in combination and over or through one another toform or enlarge the anterior percutaneous tract. The anteriorpercutaneous tract can be enlarged using one or more of the dilatorsdepicted in FIGS. 20 and 21.

A guide assembly that is employed as shown in FIGS. 22 and 23 ispreferably formed of a rounded or blunt tip occluder 62 fitted throughthe lumen of a percutaneous tubular member 70. A guidewire 80 is alsoincluded in tool set 60 that can be inserted through and also functionas an occluder of the lumen 74 of percutaneous tubular member 70.

The percutaneous tubular member 70 preferably comprises a 9–18 gaugeneedle shaft 72 enclosing a needle lumen 74 and extending between abeveled needle distal end 76 and a needle proximal end hub 78. Thetubular member lumen 74 is dimensioned in diameter to receive the blunttip occluder shaft 68 and the guidewire 80. The tubular member shaft 72is dimensioned in length to allow the distal end blunt tip 64 toprotrude from the distal end opening of the tubular member lumen 74 whenthe occluder proximal end 66 abuts the needle proximal hub 78 as shownin FIGS. 22 and 23. The needle proximal end hub 78 is preferablyremovable from the needle shaft 72 to enable passage of other tubularmembers over needle shaft 72.

The guidewire 80 illustrated in FIG. 13 has a threaded screw-in tip 82having screw threads that are adapted to be screwed into vertebral boneat various steps of the process of forming the anterior tract 26, theTASIF axial bore, and the insertion of an anterior TASIF spinal implantover the guidewire 80 as described below. The guidewire 80 is preferablyformed of a kink resistant stainless steel or nickel-titanium alloy wirehaving an outer diameter of about 0.038 inches to 0.120 inches (about1.0–3.0 mm) and a length of 100 cm or less. The threaded screw-in tip 82is formed at the distal end of the guidewire 80, and a removable knob 81is attached over the proximal end of the guidewire 80. The threadedscrew-in tip 82 can be rotated by rotation of the proximal knob 81 inorder to screw it into a vertebral body at the anterior target point andat the cephalad end of the anterior TASIF pilot hole as described below.Once the threaded screw-in tip is fixed, the proximal knob 81 can beremoved to allow tools and devices to be advanced from its free proximalend over the guidewire body toward the threaded screw-in tip 82 fixed tothe bone.

The guidewire distal end fixation mechanism 82 may be configured as ascrew-in tip as shown in FIG. 13 or as a hook as shown in FIGS. 18 and19 or simply of a sharpened tip that can be stabbed into the sacral boneat the anterior target point. If the guidewire 80 is employed as anoccluder of the guide assembly, then the guidewire distal end fixationmechanism 82 or 82′ is retracted into the lumen tubular member lumen 74as shown in FIG. 18 and described below in reference to FIG. 33. Thedistal guidewire fixation mechanism 82 or 82′ advanced out as shown inFIG. 19 and attached to the sacral bone when the outer tubular memberdistal end 76 or 76′ is located at the anterior target point of thesacrum.

The percutaneous tubular member distal end can be shaped in a variety ofways and can be formed with a 30 °–80° angled or beveled tip 76 or a 90°blunt 76′ as shown in FIGS. 13, 14, 18, 19, 22, 23 and 25. In the guideassembly depicted in FIGS. 13, 14, 22 and 23, the percutaneous tubularmember distal end can itself be sharpened, e.g., by the bevel as shownin FIG. 13, or blunted as shown in FIG. 14. In either case, thepercutaneous tubular member lumen is preferably occluded by the blunttip inner occluder which protrudes distally from the distal end openingof the tubular member 70 FIGS. 14–17 and blunts the percutaneous tubularmember distal end enabling it to be advanced along the anterior surfaceof the sacral bone as described below.

Alternatively, the percutaneous tubular member distal end can be shapedin a variety of ways to incorporate a variety of tubular member distaltip fixation mechanisms as shown in FIGS. 15–17 and 24, for example. Theblunt tip obdurator 60 can also be employed to blunt the percutaneoustubular member distal end fixation mechanisms 76′, 76″ and 76′″, forexample, enabling the guide assembly distal end to be advanced along theanterior surface of the sacral bone as described below.

One form of the anterior, presacral, percutaneous tract axially alignedwith the visualized AAIFL of FIGS. 1 and 3 through presacral spaceposterior to the patient's rectum comprises the presacral spacesurrounding the percutaneous tubular member 70 or the guidewire 80 thatis introduced as an occluder or after removal of the blunt tip occluder62 through the percutaneous tubular member lumen in accordance withsteps S102–S114 of FIG. 12. FIGS. 22–26 illustrate the exemplary use ofcertain ones of the tools shown in FIGS. 13–17 and described abovefollowing steps of FIG. 12 to form the anterior, presacral, percutaneoustract 26.

The surgical field is prepared as in the posterior TASIF proceduredescribed above. In step S102, an anterior skin incision 28 about 5–10mm long is made at an access point that is cephalad to the anus andalongside or inferior to the tip of the coccyx to avoid penetrating therectal wall. For example, the skin incision 28 can be made approximately2.0 cm lateral and 2.0 cm cephalad to the tip of the coccyx.

In step S104 as illustrated in FIG. 22, the blunt tip occluder 62 isfitted within tubular member lumen 74 to form the guide assembly asshown in FIG. 14, for example. The guide assembly is inserted throughthe anterior incision 28 and advanced carefully in step S106 underanterior and lateral fluoroscopic imaging visualization posterior to therectum and through the fatty tissue of the presacral space 24 until theblunt distal end 64 contacts the anterior surface of the sacrum. Then,in step S108 (also shown in FIG. 23), the blunt distal end 64 protrudingfrom the tubular member distal end 76 is advanced or “walked” cephaladalong the anterior sacrum under fluoroscopic or CT imaging visualizationin the presacral space 24 toward the anterior target point anterior tothe body of S2. During this process, care is taken to ensure that thetubular member shaft 72 displaces but does not perforate the rectum andto ensure that nerves and arteries traversing the sacrum and presacralspace 24 are not damaged. The rectum can be distended with air so thatits posterior wall can be visualized fluoroscopically or othervisualization system.

In step S110, after the anterior target point is reached, the guideassembly is axially aligned with the AAIFL. In step S112, either theoccluder or the tubular member distal end fixation mechanism ismanipulated to affix the occluder or tubular member to the sacrum at theanterior target point. In the embodiment illustrated in FIGS. 22 and 23,the blunt tip occluder 62 is retracted within the tubular member lumen74, and the tubular member angled distal end 76 is oriented to the angleof the anterior sacrum at the anterior target point as shown in FIG. 25.

In step S112, if the tubular member distal end comprises a distal endfixation mechanism 76″, 76′″ or 76″″, then tubular member distal end isadvanced to fix the fixation mechanism to sacral bone as shown in FIG.24. In step S114, the occluder is removed from the tubular member lumen74, as also shown in FIG. 24. Thus, the percutaneous, presacral,percutaneous tract comprises the presacral space surrounding the tubularmember affixed to be axially aligned with the visualized AAIFL so thatfurther tools can be introduced over or alongside the affixed tubularmember. The elongated tubular member 70 may be inflexible as a steelneedle or flexible as a small diameter catheter but having sufficientcolumn strength to allow torque or axially applied force to betransmitted to its distal end to affix the distal fixation mechanisminto sacral bone. In any case, the proximal hub 78 is removable to allowan effective over-the-wire introduction of other tools described furtherbelow.

Alternatively, when the occluder takes the form of the guidewire 80 or80′ within the tubular member lumen 74 of a blunt tipped tubular member70, the guidewire distal fixation mechanism 82, 82′ is operated in stepS112 to fix it to the sacral bone as shown, for example, in FIG. 25, anddescribed above. In the example shown in FIG. 25, the guidewire knob 81is rotated to screw the distal screw-in tip 82 into the vertebral bone,and the guidewire knob 81 is pulled off the proximal end of theguidewire 80. The tubular member 70 is retracted in step S114, leavingthe guidewire 80, 80′ axially aligned with the visualized AAIFL as shownin FIG. 26.

Thus, in this embodiment, the percutaneous, presacral, percutaneoustract comprises the presacral space surrounding the guidewire affixed tobe axially aligned with the visualized AAIFL so that further tools canbe introduced over or alongside the affixed guidewire. The guidewire maybe inflexible as a steel needle or typical surgical obdurator orflexible as a small diameter transvenous or arterial or neural guidewirebut having sufficient column strength to allow torque or axially appliedforce to be transmitted to its distal end to affix the distal fixationmechanism into sacral bone.

Then, to the extent necessary, the tissue surrounding the skin incision28 and the presacral space 24 surrounding the extended guidewire 80 orthe tubular member 70 are dilated in step S118 and the rectum is pushedaside without perforating it. A variety of tissue dilators that can befitted over the extended guidewire 80 or the tubular member 70 areprovided in step S116.

One form of tissue dilator comprises a balloon catheter 84 illustratedin FIG. 13. Only the distal portion of the balloon catheter 84 isdepicted in FIG. 13, and it comprises a balloon catheter shaft 86supporting the expandable balloon 90 and enclosing a balloon shaft lumen88 and a balloon inflation lumen 92. The balloon catheter shaft lumen 88extends the length of the balloon catheter shaft 86 and terminates at adistal lumen end opening at balloon catheter distal end 94 to allow theguidewire 80 or the tubular member 70 to be received within it. Theballoon catheter shaft lumen 88 facilitates advancement of the ballooncatheter shaft 86 over the previously placed guidewire 80 or tubularmember 70 while the balloon 90 is deflated. The proximal portion of theballoon catheter 84 may take any of the conventional forms comprising ahub for passing the guidewire 80 or tubular member 70 and a side portfor providing inflation fluid to and removing fluid from the ballooninflation lumen 92 to inflate and deflate the balloon 90.

Alternatively, a set of 10F, 12F, 14F, et. seq., tissue dilators 340,350 shown in FIGS. 20–21 may also be used, to the extent necessary overthe guidewire 80 or tubular member 70 (or over a first anterior tractsheath 120 as described below). A single dilator 340 having a gradualtaper 342 at the distal end is shown in FIG. 20 to dilate sacral tissueto a first anterior tract diameter. A further dilator 350 having afurther taper 352 is shown in FIG. 21 advanced over the first tissuedilator 340 to further expand the anterior tract diameter.

The balloon catheter 84 or the dilator(s) 340, 350 is employed to dilatethe presacral tissue and to facilitate the optional insertion of theenlarged diameter anterior tract sheath 96 depicted in FIG. 13 or 196depicted in FIGS. 30 and 31, in accordance with steps S120 and S122. Theenlarged diameter anterior tract sheath 96 is preferably formed of athin, relatively rigid, metal or plastic tube that is long enough toextend from the skin incision to the anterior target point through thepresacral space and. The enlarged diameter anterior tract sheath 96 hasan anterior tract sheath lumen 98 and a beveled distal end 97 that is atan angle to the sheath axis. Alternatively, the enlarged diameteranterior tract sheath 196 is formed with an anterior tract sheath distalfixation mechanism 197 of the types employed in the variations of thetubular member 70 described above. A distal threaded tip fixationmechanism 197 is illustrated in FIGS. 30 and 31. Preferably, thediameter of the anterior tract sheath lumen 98, 198 is about 15 mm or36F, and tract sheath 96, 196 is about 20 cm long.

The balloon catheter dilator or the dilators 340, 350 are used over theguidewire or over the tubular member of the guide assembly to center theenlarged diameter anterior tract sheath 96 or 196 and to easeintroduction of the enlarged diameter anterior tract sheath 96 or 196past the posterior abdominal wall.

In use of the first embodiment, the enlarged diameter anterior tractsheath 96 is advanced through the presacral space 24 over the inflatedballoon 90 or the dilator(s) 340, 350, and the beveled distal end 97 isaligned with the typical angle of the anterior surface of the sacrum atthe anterior target point as shown in FIG. 28. The anterior tract sheath96 is thereby axially aligned with the AAIFL, and the anterior tractsheath lumen 98 forms the anterior tract 26 shown in FIG. 1.

In use of the second embodiment, the anterior tract sheath 196 isadvanced through the presacral space 24 over the inflated balloon 90 orthe dilator(s) 340, 350 as shown in FIG. 30, and the threaded tip distalend 197 is screwed into the sacral bone at the anterior target point asshown in FIG. 31. The anterior tract sheath 196 is thereby axiallyaligned with the AAIFL, and the anterior tract sheath lumen 198 formsthe anterior tract 26 shown in FIG. 1.

The balloon 90 is then deflated, and the balloon catheter 84 and theguidewire 80 are withdrawn from tract sheath lumen 98, 198.Alternatively, the dilator(s) 340, 350 and the guidewire 80 arewithdrawn from tract sheath lumen 98. The anterior tract 26 of theanterior tract sheath 96, 196 is employed in the steps of FIG. 6 informing the anterior TASIF axial bore (step S200), the performance ofthe optional discectomy or disc augmentation (step S300), and in theimplantation of the TASIF spinal implant in each such bore (step S400).

FIG. 32 shows alternative particular steps of step S100 for attaching aguidewire 80, 80′ to the anterior target point to form an anterior,presacral, percutaneous tract maintained in axial alignment with theAAIFL as shown in FIG. 26. The guide assembly comprising the occluder 62and tubular member 70 are provided, assembled, advanced and axiallyaligned with the AAIFL in steps S504–S512 as depicted in FIGS. 22 and23. The occluder 62 is withdrawn from the tubular member lumen 74 instep S514, and the guidewire 80, 80′ is provided in step S516. Theguidewire 80, 80′ is advanced through the tubular member lumen 74 instep S516 and S518 as shown in FIGS. 18 and 25. Then, the guidewiredistal end fixation mechanism 82, 82′ is advanced from the distal endopening of the tubular member lumen 74 and affixed to the sacral bone asshown in FIGS. 19 and 25. The tubular member 62 is then withdrawn instep S522, leaving the guidewire 80, 80′ affixed and extending axiallyin alignment with the AAIFL through the presacral space. Steps S116–S122of FIG. 12 can then be optionally performed as described above.

FIG. 32 shows alternative particular steps of attaching a guidewire 80,80′ to the anterior target point to form an anterior, presacral,percutaneous tract maintained in axial alignment with the AAIFL. In thisembodiment, the guidewire 80, 80′ is inserted into the tubular memberlumen 74 to form the guide assembly in step S604. The guidewire distalfixation mechanism 82, 82′ is retracted proximally within the tubularmember lumen 74, and the tubular member distal end 76′ is preferablyblunt as shown in FIG. 18, for example. The guide assembly is advancedand axially aligned in steps S606–S610 in the manner shown in FIGS. 22and 23. Then, the guidewire distal end fixation mechanism 82, 82′ isadvanced from the distal end opening of the tubular member lumen 74 andaffixed to the sacral bone as shown in FIGS. 19 and 25. The tubularmember 62 is then withdrawn in step S522, leaving the guidewire 80, 80′affixed and extending axially in alignment with the AAIFL through thepresacral space. Steps S116–S122 of FIG. 12 can then be optionallyperformed as described above.

Three forms of anterior percutaneous tracts 26 are described abovefollowing alternative and optional steps of FIG. 12, that is, over theguidewire 80, 80′ or over the tubular member 70, 70′, 70″, 70′″, 70″″(optionally dilated), or through the anterior tract sheath lumen 96,196. In each case, one or more anterior TASIF axial bores 22, 22′ asshown in FIGS. 4 and 5 can be formed through these three forms ofanterior percutaneous tracts 26. The anterior TASIF axial bores 22, 22′can be formed using the anterior TASIF axial bore hole boring tools 40and 40′ of FIGS. 44 and 45 starting at or around the anterior targetpoint and extending along or parallel with the AAIFL in the cephaladdirection to bore one or more relatively straight or curved anteriorTASIF axial bore through S1 and into or through L5 and optionallythrough further lumbar vertebrae and any damaged or intactintervertebral discs.

Further embodiments of anterior, presacral. percutaneous tracts 26 arepossible using a first anterior tract sheath 120 and pilot forming toolor drill 112 illustrated in FIG. 13. FIGS. 34–39 show steps of formingan anterior pilot hole 150 tracking the AAIFL and attaching a guidewire80, 80′ to the cephalad end of the pilot hole 150 to form an anterior,presacral, percutaneous tract about the guidewire 80, 80′ maintained inaxial alignment with the AAIFL. An intermediate anterior tract sheath orthread-tipped sheath 120 that is smaller in diameter than the enlargedtract sheath 96 and a boring tool, e.g., drill bit 112, sized to fitthrough the first tract sheath lumen 126, are provided in the tool set60 that are used to form the pilot hole 150. The drill bit 112 ispreferably a 1–5 mm diameter steel drill that is about 30 cm long havingdrill threads 116 at its sharpened end and is intended to be attached atits other end to a drill to be used to form a pilot hole along AAIFL.The intermediate anterior tract sheath 120 is preferably formed with atract sheath distal end fixation mechanism, e.g., a distal screw thread122, coupled to the distal end of sheath body 124. The thread-tippedsheath lumen 126 extends the length of the thread-tipped sheath 120through both the distal screw thread 122 and the thread-tipped sheathbody 124. The thread-tipped sheath 120 is preferably about 25 cm longand has an outer diameter or about 6.0–9.0 mm and an inner lumendiameter of about 3.5–5.5 mm. The thread-tipped sheath body 126 ispreferably formed of a somewhat stiff plastic, e.g. urethane, and thedistal screw thread 122 is preferably formed of a metal e.g., stainlesssteel. The distal screw thread 122 and distal end of the thread-tippedsheath body 126 are preferable thermally attached using an overlappingjoinder. Again, alternative fixation mechanisms can be employedincluding the teeth 76′″ depicted in FIG. 16.

The intermediate anterior tract sheath 120 is adapted to be placeddirectly through the anterior tract and fixed in position in axialalignment with the AAIFL as shown in FIG. 36. However, the intermediateanterior tract sheath 120 can be advanced over the previously fixed andaxially aligned guidewire 80, 80′ or tubular member 70″, 70′″ or 70′″ orover a dilator over either as indicated in step S804. For convenience,use of a fixed guidewire 80 and advancement of the thread-tipped sheath120 over the guidewire 80 are illustrated in FIG. 35. The guidewire 80,80′ is attached to the sacral bone in any of the above-described waysleaving it in place as shown in FIG. 26.

In step S804, the thread-tipped sheath 120 is advanced over theguidewire 80, 80′ until its distal screw thread 122 contacts the sacrumat the anterior target point. The thread-tipped sheath body 124 isaxially aligned with the AAIFL, and the proximal end of thethread-tipped sheath body 124 is rotated to screw or thread the distalscrew thread 122 into the sacrum bone as shown in FIG. 36. Then, in stepS808, the distal screw-in tip 82 of the guidewire 80 is unscrewed fromthe sacrum bone and withdrawn from the sheath lumen 126 as also shown inFIG. 36. The guidewire proximal end may be reattached to the knob 81 tofacilitate rotation of the guidewire 80 to unscrew the screw-in tip 82from the sacral bone.

In step S812, the drill bit 112 is advanced through the sheath lumen 126and is rotated by a drill motor (not shown) to drill out a pilot hole150 aligned with the AAIFL under visualization cephalad through S1, L4and L5, and the intervening discs as shown in FIG. 37. The drill bit 112is then withdrawn from the pilot hole 150 and sheath lumen 126.

The thread-tipped sheath lumen 126 provides access from the skinincision to the pilot hole 150 to avoid blood infiltration into thepilot hole 150. Instruments, e.g., an endoscope, can be advancedtherethrough and into the pilot hole to visualize the condition of thevertebral bodies and the discs traversed by the pilot hole 150. Inaddition, procedures including discectomy, disc augmentation andvertebroblasty can be performed by instruments advanced into the pilothole 150 through the thread-tipped sheath lumen 126.

In step S814, the screw-in tip guidewire 80 is advanced through thesheath lumen 126 and the pilot hole 150 in step S814. The guidewireproximal end may be reattached to the knob 81, and the guidewire 80 isrotated to screw the screw-in tip 82 into vertebral bone at the cephaladend of the pilot hole 150 in step S816. The guidewire knob 81 is thenremoved, if reattached, and the proximal end of the thread-tipped sheathbody 124 is rotated to unscrew the distal screw thread 122 from thesacral bone in step S818. The thread-tipped sheath 120 is then withdrawnfrom the presacral space over the guidewire 80. The guidewire 80 remainsattached to and extending through the pilot bore 150 and presacral space24 as shown in FIG. 39 thereby providing an anterior tract extendingbetween the cephalad end of the pilot hole 150 and the skin incision 28.The pilot hole 150 may be expanded by a bore forming tool introducedover the guidewire 80.

FIGS. 40–43 show further method steps of dilating the presacral tissuearound the affixed guidewire 80 of FIG. 39 and the insertion of anenlarged diameter anterior tract sheath 96 through the dilated presacralspace to form the anterior, presacral, percutaneous tract 26 comprisingthe anterior tract sheath lumen 98. In the exemplary illustration ofthis surgical procedure, the balloon catheter 84 is provided in stepS818 and employed in FIGS. 41 and 42 to dilate the sacral tissue, but itwill be understood that other dilators, e.g., dilators 340, 350 could beemployed alternatively.

In step S820, the deflated dilatation balloon catheter 84 is advancedover the guidewire 80 until its distal end 94 abuts or enters the pilothole 150 and is aligned axially with the AAIFL. The balloon 90 is thenexpanded under pressure to its rigid expanded diameter, and itsexpansion dilates the presacral tissue in the presacral space 24 asshown in FIG. 41. Then, in step S822, the anterior tract sheath 96 isinserted through the presacral space 24 over the expanded balloon 90 androtated as necessary to aligned the shaped distal end 97 with the angleof the sacrum surrounding the pilot hole 150 as shown in FIG. 42

If an enlarged diameter, threaded tip, anterior tract sheath 196 issubstituted for tract sheath 96 in step S822, it is advanced over theinflated balloon and fixed to the sacral bone surrounding the pilot hole150 in the manner shown in FIGS. 30 and 31 in step S826.

The balloon 90 is deflated, and the balloon catheter 84 is withdrawnover the guidewire 80 from the anterior tract 26 in step S828 after theenlarged diameter, anterior tract sheath 96 or 196 is positioned orfixed. The guidewire 80 is optionally detached and withdrawn from thepilot hole 150 and tract sheath lumen 98, 198 in step S830. Step S100 ofFIG. 6 is then completed, forming the anterior tract 26 aligned with theAAIFL and extending percutaneously to axially access the lumbarvertebrae as shown.

Step S200 of FIG. 6 is then also completed if the diameter of the pilothole 150 is sufficient to be used as the TASIF axial bore for completionof steps S300 and S400. As noted above, step S300 of FIG. 6 may beperformed using the pilot hole 150 formed in step S100 or using theenlarged diameter, anterior TASIF axial bore 152 formed using theanterior tracts 26 formed by any of the above-described procedures. Thetools employed in the performance of step S300 may or may not requireover-the-wire insertion using the guidewire 80. The guidewire proximalend may be reattached to the knob 81 to facilitate rotation of theguidewire 80 to unscrew the screw-in tip 82 from the vertebral body andremoval of the guidewire 80 if it is not to be used in the completion ofsteps S300 and S400.

Step S200 can be preferably performed following step S830 using ananterior axial bore forming tool set comprising the guidewire 80attached to the cephalad end of the pilot hole and an enlarging tool 140or one of the bore drilling tools 40 of FIG. 44 or 40′ of FIG. 45.Either a straight or a curved anterior TASIF axial bore may be formed.One anterior approach to forming the anterior TASIF axial bore isillustrated in FIG. 46 wherein an enlarged bore forming drill bit orreamer 140 is advanced over the guidewire 80 to enlarge the pilot holediameter and form the larger diameter anterior TASIF axial bore.Consequently, the guidewire 80 is left in place to perform step S200using the enlarging tool 140. The larger diameter enlarging tool, e.g.,a drill bit, ranguer or tap 140, used in step S200 preferably bores a10.0 mm diameter anterior TASIF axial bore. The guidewire screw-in tip82 can then be unscrewed from the vertebral bone at the cephalad end ofthe anterior TASIF axial bore 152 as described above, if it is notneeded to perform steps S300 and S400. The above-described procedure maybe repeated to form two or more parallel anterior TASIF axial bores.

The longitudinal, TASIF axial bore that is formed in steps S100 and S200of FIG. 6 and all of the embodiments thereof described above starts inthe sacrum at the anterior target point and extends upwardly or cephaladthrough the vertebral body of S1 or S2 and through the cephaladvertebral bodies including L5 and L4 and the intervening discs denotedD4 and D5 in FIG. 1. Discs D4 and D5 are usually damaged or havedegenerated between lumbar spine vertebrae and cause the painexperienced by patients requiring intervention and fusion of thevertebrae. A visual inspection, discectomy and/or disc augmentationand/or vertebroblasty may be performed pursuant to step S300 of FIG. 6through the axially aligned anterior TASIF axial bore and anterior tract26 to relieve the patient's symptoms and aid in the fusion achieved by aspinal implant or rod.

Although particular embodiments of the invention have been describedherein in some detail, this has been done for the purpose of providing awritten description of the invention in an enabling manner and to form abasis for establishing equivalents to structure and method steps notspecifically described or listed. It is contemplated by the inventorsthat the scope of the limitations of the following claims encompassesthe described embodiments and equivalents thereto now known and cominginto existence during the term of the patent. Thus, it is expected thatvarious changes, alterations, or modifications may be made to theinvention as described herein without departing from the spirit andscope of the invention as defined by the appended claims.

1. A method of providing access for introduction of instruments to aseries of adjacent vertebrae located within a human lumbar and sacralspine having an anterior aspect, a posterior aspect and an axial aspect,the vertebrae separated by intact or damaged spinal discs, the methodcomprising: from a skin incision, accessing an anterior or posteriorsacral position of a sacral vertebra that is aligned with a visualized,trans-sacral axial fusion/instrumentation line extending in said axialaspect through the series of adjacent vertebral bodies; forming apercutaneous tract extending from the skin incision to an anterior orposterior sacral position of a sacral vertebra having a tract axisaligned with said visualized, trans-sacral axial instrumentation/fusionline providing axial guidance for said instruments introduced over orthrough said percutaneous tract to said anterior or posterior sacralposition; and positioning an instrumentation guide in the tract, toguide the instruments to the sacral position.
 2. The method of claim 1,wherein said instruments comprise a boring tool, and further comprising:from said accessed sacral position, boring a trans-sacral axialinstrumentation/fusion bore through the sacrum and into at least onevertebrae and any intervertebral disc in alignment with said visualized,trans-sacral axial instrumentation/fusion line employing said boringtool advanced over or through said percutaneous tract to said anterioror posterior sacral position.
 3. The method of claim 1, wherein the stepof forming a percutaneous tract further comprises forming a posteriorpercutaneous tract to access the posterior presacral position of asacral vertebra in alignment with a visualized, curved, posterior axialinstrumentation/fusion line extending in said axial aspect initiallylaterally through the sacral vertebra and then following the curvatureof the spine through a series of adjacent cephalad vertebral bodies. 4.The method of claim 3, wherein the step of forming a posteriorpercutaneous tract comprises: providing a posterior tract sheath havinga tract sheath axis and tract sheath lumen extending between tractsheath proximal and distal ends, the tract sheath distal end formed witha bone attachment mechanism; advancing the tract sheath distal end tosaid posterior presacral position with said tract sheath axis alignedwith a sacral end of said visualized, curved, posterior axialinstrumentation/fusion line; and attaching the bone attachment mechanismat the tract sheath distal end to sacral bone to align the tract sheathaxis with the sacral end of said visualized, curved, posterior axialinstrumentation/fusion line, whereby the posterior tract sheath extendsthrough the skin incision and to the posterior presacral position. 5.The method of claim 3, wherein the accessing step further comprises:drilling a pilot hole of a first diameter from a presacral penetrationposition along said axial instrumentation/fusion line within and axiallythrough said series of vertebral bodies and intervening spinal discs toa cephalad pilot hole end within a vertebral body; providing a guidewirehaving a guidewire proximal end and a guidewire distal end; andextending the guidewire through said presacral space and through saidpilot hole to locate the distal end of said guidewire at the cephaladpilot hole end.
 6. The method of claim 5, wherein the guidewire distalend is fitted with a distal fixation mechanism, and the extending stepfurther comprises: attaching the distal fixation mechanism of theguidewire distal end to the vertebral body at the cephalad pilot holeend.
 7. The method of claim 3, wherein the step of forming a posteriorpercutaneous tract comprises: providing a guidewire having a guidewireproximal end and a guidewire distal end fitted with a distal fixationmechanism; attaching the distal fixation mechanism of the guidewiredistal end to the sacral bone at the sacral position; and axiallyaligning the guidewire with the axial instrumentation/fusion line.
 8. Amethod of providing access to a series of adjacent vertebrae locatedwithin a human lumbar and sacral spine having an anterior aspect, aposterior aspect and an axial aspect, the vertebrae separated by intactor damaged spinal discs, the method comprising: from a skin incision,accessing an anterior or posterior sacral position of a sacral vertebrathat is aligned with a visualized, trans-sacral axialfusion/instrumentation line extending in said axial aspect through theseries of adjacent vertebral bodies; forming an anterior, presacral,percutaneous tract through the patient's presacral space to access ananterior presacral position of a sacral vertebra in alignment with avisualized, anterior axial instrumentation/fusion line extending in saidaxial aspect through the series of adjacent vertebral bodies; andpositioning a tubular sleeve in the tract.
 9. The method of claim 8,wherein the accessing step further comprises: making an incision throughthe patient's skin adjacent to the coccyx aligned with the visualizedanterior axial instrumentation/fusion line; and forming a percutaneouspathway through presacral tissues in presacral space between the skinincision and an anterior target point of the anterior sacrum alignedwith the visualized anterior axial instrumentation/fusion line; and thestep of forming a percutaneous tract further comprises expanding thepercutaneous pathway to form the anterior, presacral, percutaneous tractthrough the patient's skin and presacral space aligned with thevisualized anterior axial instrumentation/fusion line to provide workingspace and exposure of the anterior sacrum.
 10. The method of claim 8,wherein the accessing step further comprises: providing a blunted tiptubular member having a tubular member body and blunt tubular membertip; and inserting the blunted tip tubular member through the incisionand advancing the blunt tubular member tip along the anterior surface ofthe sacrum under visualization until the tubular member tip is at ananterior target point of a selected sacral vertebrae and the tubularmember body is aligned with the visualized anterior axialinstrumentation/fusion line and extends percutaneously.
 11. The methodof claim 8, wherein the accessing step further comprises: providing ablunted tip tubular member having a tubular member lumen within atubular member body extending from a proximal tubular member end to adistal tubular member end and a blunt tipped occluder fitted into thetubular member to extend distally from the distal tubular member end;and inserting the blunted tip tubular member through the incision andadvancing the blunt tubular member tip along the anterior surface of thesacrum under visualization until the tubular member tip is at ananterior target point of a selected sacral vertebrae and the tubularmember body is aligned with the visualized anterior axialinstrumentation/fusion line and extends percutaneously; and the step offorming the anterior, presacral, percutaneous tract further comprises:removing the blunt tipped occluder from the tubular member lumen;providing a guidewire having a guidewire body extending between aguidewire proximal end and a guidewire distal end and a guidewirefixation mechanism for penetrating and affixing to bone at the guidewiredistal end; extending the guidewire through said tubular member lumen tolocate the guidewire distal end at the anterior target point; affixingthe guidewire fixation mechanism to bone at the anterior target point;and removing the tubular member body, whereby the guidewire provides apercutaneous tract over or through the tubular member from the incisionsite to the anterior target point and aligned axially with saidvisualized anterior axial instrumentation/fusion line.
 12. The method ofclaim 11, further comprising: dilating the tissue surrounding theguidewire body; providing an enlarged diameter anterior tract sheathhaving a tract sheath lumen extending between proximal and distalanterior tract sheath ends; and inserting said anterior tract sheaththrough said enlarged anterior tissue tract over said guidewire toposition said enlarged diameter anterior tract sheath distal end againstthe anterior sacrum with the anterior tract sheath lumen aligned axiallywith the visualized anterior axial instrumentation/fusion line.
 13. Themethod of claim 11, further comprising: providing a dilatation ballooncatheter; providing an enlarged diameter anterior tract sheath having atract sheath lumen extending between proximal and distal anterior tractsheath ends; with the guidewire aligned with the anterior axialinstrumentation/fusion line, advancing the dilatation balloon catheterover the guidewire to locate a deflated balloon of the dilatationballoon catheter extending through presacral space; expanding thedeflated balloon to an expanded balloon diameter to dilate the presacraltissue between the anterior sacral surface and the skin incision;advancing the enlarged diameter anterior tract sheath lumen over theexpanded balloon to position the anterior tract sheath between theanterior target point and the skin incision and in alignment with theanterior axial instrumentation/fusion line; and deflating the balloonand withdrawing the balloon catheter from the anterior tract sheathlumen, whereby the anterior tract sheath lumen provides the anterior,presacral, percutaneous tract through the patient's presacral space. 14.The method of claim 11, further comprising: providing a tissue dilatorhaving a dilator body of a dilation diameter and a dilator lumen havinga dilator lumen diameter sized to receive the guidewire and extendingbetween proximal and distal dilator body ends; passing the dilator overthe guidewire toward the anterior target point to dilate the tissuesurrounding the guidewire body; and withdrawing the tissue dilator fromthe guidewire body upon completion of dilation.
 15. The method of claim14, further comprising: providing an enlarged diameter anterior tractsheath having a tract sheath lumen extending between proximal and distalanterior tract sheath ends; and inserting said anterior tract sheaththrough said enlarged anterior tissue tract to position said enlargeddiameter anterior tract sheath distal end against the anterior sacrumwith the anterior tract sheath lumen aligned axially with the visualizedanterior axial instrumentation/fusion line.
 16. The method of claim 11,further comprising: providing a first tissue dilator having a dilatorbody of a dilation diameter and a dilator lumen having a dilator lumendiameter sized to receive the guidewire and extending between proximaland distal first tissue dilator body ends; providing a second tissuedilator having a dilator body of a dilation diameter and a dilator lumenhaving a dilator lumen diameter sized to receive the first tissuedilator body and extending between proximal and distal second tissuedilator body ends; passing the first tissue dilator over the guidewiretoward the anterior target point to dilate the tissue surrounding theguidewire body; passing the second tissue dilator over first tissuedilator and the guidewire toward the anterior target point to furtherdilate the tissue surrounding the guidewire body; and withdrawing thefirst and second tissue dilators from the guidewire body upon completionof dilation.
 17. The method of claim 16, further comprising: providingan enlarged diameter anterior tract sheath having a tract sheath lumenextending between proximal and distal anterior tract sheath ends; andinserting said anterior tract sheath through said enlarged anteriortissue tract to position said enlarged diameter anterior tract sheathdistal end against the anterior sacrum with the anterior tract sheathlumen aligned axially with the visualized anterior axialinstrumentation/fusion line.
 18. The method of claim 11, furthercomprising: providing an enlarged diameter tubular anterior tract sheathhaving a tract sheath lumen extending between proximal and distalanterior tract sheath ends and an anterior tract sheath distal fixationmechanism adapted to attach said enlarged diameter anterior tract sheathto sacral bone; inserting said enlarged diameter anterior tract sheaththrough said enlarged anterior tissue tract over said guidewire toposition said enlarged diameter anterior tract sheath distal end againstthe anterior sacrum with the anterior tract sheath lumen aligned axiallywith the visualized anterior axial instrumentation/fusion line; andoperating said anterior tract sheath distal fixation mechanism to attachsaid anterior tract sheath to sacral bone with the anterior tract sheathlumen aligned axially with the visualized anterior axialinstrumentation/fusion line.
 19. The method of claim 18, wherein theanterior tract sheath fixation mechanism comprises distal screw threadsencircling the distal anterior tract sheath end adapted to be screwedinto bone, and the step of affixing the anterior tract sheath distalfixation mechanism to bone at the anterior target point comprisesrotating the anterior tract sheath body in a proximal section extendingfrom the skin incision to screw the distal screw threads into sacralbone.
 20. A surgical operating system for farming a percutaneous pathwayfrom a skin incision generally axially aligned with a series of adjacentvertebrae located within a human lumbar and sacral spine having ananterior aspect, a posterior aspect and an axial aspect, the vertebraeseparated by intact or damaged spinal discs, the system comprising:guide means operable from a skin incision for accessing an anterior orposterior sacral position of a sacral vertebra that is aligned with avisualized, trans-sacral axial instrumentation/fusion line extending insaid axial aspect through the series of adjacent vertebral bodies; andtract means defining a percutaneous tract having a tract axis alignedwith said visualized, trans-sacral axial instrumentation/fusion line andextending from the skin incision to the accessed sacral position tofacilitate surgical procedures aligned with said visualized,trans-sacral axial instrumentation/fusion line.
 21. A surgical operatingsystem for forming a percutaneous pathway from a skin incision generallyaxially aligned with a series of adjacent vertebrae located within ahuman lumbar and sacral spine having an anterior aspect, a posterioraspect and an axial aspect, the vertebrae separated by intact or damagedspinal discs, the system comprising: an elongated guide assemblyextendible from a skin incision for accessing an anterior or posteriorsacral position of a sacral vertebra that is aligned with a visualized,trans-sacral axial instrumentation/fusion line extending in said axialaspect through the series of adjacent vertebral bodies; and a dilatoradapted to dilate tissue surrounding the elongated guide assembly toform an enlarged percutaneous tract that is aligned with a visualized,trans-sacral axial instrumentation/fusion line.
 22. The system of claim21, wherein said elongated guide assembly further comprises: anelongated tubular member enclosing a tubular member lumen extendingbetween a tubular member proximal end and a tubular member distal end;and an occluder extending between an occluder proximal end and anoccluder distal end adapted to be extended through said tubular memberlumen.
 23. The system of claim 21, further comprising a tract sheathadapted to be fitted over said elongated guide assembly followingdilation of tissue, the tract sheath having a tract sheath lumen formingthe percutaneous tract having a tract axis aligned with said visualized,trans-sacral axial instrumentation/fusion line extending from the skinincision to the accessed sacral position.
 24. Apparatus for obtainingaccess to and through a series of adjacent vertebrae located within ahuman lumbar and sacral spine having an anterior aspect, a posterioraspect and an axial aspect, the vertebrae separated by intact or damagedspinal discs, the apparatus comprising: means for exposing a sacralposition of a sacral vertebra in alignment with a visualized,trans-sacral axial instrumentation/fusion line extending in said axialaspect through the series of adjacent vertebral bodies; means operablefrom the exposed sacral position for boring a trans-sacral pilot holeextending along said axial instrumentation/fusion line cephalad andaxially through the vertebral bodies of said series of adjacentvertebrae and any intervening spinal discs to a pilot hole cephalad end;and a guidewire having a guidewire body extending between a guidewireproximal end and a guidewire distal end having a guidewire fixationmechanism at the guidewire distal end adapted to be advanced into thepilot hole and affixed to vertebral bone at the cephalad end of thepilot hole.
 25. A surgical operating system for forming a percutaneouspathway from a skin incision generally axially aligned with a series ofadjacent vertebrae located within a human lumbar and sacral spine havingan anterior aspect, a posterior aspect and an axial aspect, thevertebrae separated by intact or damaged spinal discs, the systemcomprising: guide means operable from a skin incision through apatient's skin and exposing a posterior, presacral position of a sacralvertebra in alignment with a visualized, curved, posterior axialinstrumentation/fusion line extending in said axial aspect initiallylaterally through the sacral vertebra and then following the curvatureof the spine through a series of adjacent cephalad vertebral bodies foraccessing a posterior sacral position of a sacral vertebra that isaligned with the visualized, trans-sacral axial instrumentation/fusionline extending in said axial aspect through the series of adjacentvertebral bodies; and tract means defining a percutaneous tract having atract axis aligned with said visualized, trans-sacral axialinstrumentation/fusion line and extending from the skin incision to theaccessed sacral position to facilitate surgical procedures aligned withsaid visualized, trans-sacral axial instrumentation/fusion line.
 26. Thesystem of claim 25, wherein the tract means comprises a tubularposterior tract sheath forming a posterior percutaneous tract throughthe patient's presacral space to access the posterior presacral positionof a sacral vertebra in alignment with the visualized, anterior axialinstrumentation/fusion line extending in said axial aspect through theseries of adjacent vertebral bodies to enable boring a curved posterioraxial bore extending along said posterior axial instrumentation/fusionline cephalad through the vertebral bodies of said series of adjacentvertebrae and any intervening spinal discs.
 27. The system of claim 26,wherein the tubular posterior tract sheath has a tract sheath lumenextending between proximal and distal posterior tract sheath ends and aposterior tract sheath distal fixation mechanism adapted to attach saidposterior tract sheath distal end to sacral bone with the posteriortract sheath lumen aligned axially with the visualized posterior axialinstrumentation/fusion line.
 28. A method of providing access to aseries of adjacent vertebrae located within a lumbar and sacral spinehaving an anterior aspect, a posterior aspect and an axial aspect, thevertebrae separated by intact or damaged spinal discs, the methodcomprising: making an incision through the patient's dermal entry sitealigned with a visualized curved, posterior axial instrumentation/fusionline extending in said axial aspect through the series of adjacentvertebral bodies; providing a guide assembly having a guide assemblybody extending between guide assembly proximal and distal ends, saidguide assembly comprising a guide tubular member having a tubular memberlumen within a tubular member body extending between proximal and distaltubular member ends; advancing the guide assembly through the incisionto locate the guide assembly distal end against the posterior surface ofthe sacrum; further advancing the guide assembly distal end undervisualization until the guide assembly distal end is at a posteriortarget point of a selected sacral vertebrae and the guide assembly bodyis aligned with the visualized curved, posterior axialinstrumentation/fusion line and extends percutaneously to the guideassembly proximal end; and advancing the tubular member distal endagainst the posterior target point, whereby the tubular member providesa percutaneous tract over or through the tubular member from the dermalentry site to the posterior target paint.
 29. The method of claim 28,further comprising the step of determining the dermal entry site bymapping the curved, posterior axial instrumentation/fusion line.
 30. Themethod of claim 29, wherein the step of mapping the curved, posterioraxial instrumentation/fusion line comprises performing a CT scan. 31.The method of claim 29, wherein the step of mapping the curved,posterior axial instrumentation/fusion line comprises performing a MRIstudy.
 32. The method of claim 28, further comprising the step ofperforming a laminectomy at the posterior surface of the sacrum.
 33. Themethod of claim 32, further comprising the step of retracting the thecalsac and nerve roots exposed by the laminectomy.
 34. The method of claim28, wherein the step of providing a guide assembly further comprisesproviding a beveled tip tubular member having a tubular member lumenwithin a tubular member body extending from a proximal tubular memberend to a distal tubular member end as said tubular member.
 35. Themethod of claim 28, wherein the step of providing a guide assemblyfurther comprises providing a blunt tip tubular member having a tubularmember lumen within a tubular member body extending from a proximaltubular member end to a distal tubular member end of said tubularmember.
 36. The method of claim 28, wherein the step of providing aguide assembly further comprises providing a trocar having a trocarlumen within a trocar body extending from a proximal trocar end to adistal trocar end of said tubular member.
 37. The method of claim 28,wherein the step of providing a guide assembly further comprisesproviding a guide sheath having a guide sheath lumen within a guidesheath body extending from a proximal guide sheath end to a distal guidesheath end of said tubular member.
 38. A method of providing access to aseries of adjacent vertebrae located within a lumbar and sacral spinehaving an anterior aspect, a posterior aspect and an axial aspect, thevertebrae separated by intact or damaged spinal discs, the methodcomprising: making an incision through the patient's dermal entry sitealigned with a visualized curved, posterior axial instrumentation/fusionline extending in said axial aspect through the series of adjacentvertebral bodies; providing a guide assembly having a guide assemblybody extending between guide assembly proximal and distal ends, saidguide assembly comprising: a guide tubular member having a tubularmember lumen within a tubular member body extending between proximal anddistal tubular member ends; and a guidewire having a guidewire bodyextending between a guidewire proximal end and a guidewire distal endhaving a guidewire fixation mechanism for penetrating and affixing tobone at the guidewire distal end; inserting the guidewire through saidtubular member lumen to locate the guidewire distal end retracted withinsaid tubular member lumen and said guidewire proximal end extendingproximally from said tubular member proximal end; advancing the guideassembly through the incision to located the guide assembly distal endagainst the posterior surface of the sacrum; further advancing the guideassembly distal end under visualization until the guide assembly distalend is at a posterior target point of a selected sacral vertebrae andthe guide assembly body is aligned with the visualized curved, posterioraxial instrumentation/fusion line and extends percutaneously to theguide assembly proximal end; extending the guidewire through saidtubular member lumen into contact with the sacrum; affixing theguidewire fixation mechanism to sacral bone at the posterior targetpoint; and removing the tubular member, whereby the attached guidewireprovides a percutaneous tract for over the wire passage extending fromthe dermal entry site to the posterior target point.
 39. The method ofclaim 38, further comprising the step of determining the dermal entrysite by mapping the curved, posterior axial instrumentation/fusion line.40. The method of claim 39, wherein the step of mapping the curved,posterior axial instrumentation/fusion line comprises performing a CTscan.
 41. The method of claim 39, wherein the step of mapping thecurved, posterior axial instrumentation/fusion line comprises performinga MRI study.
 42. The method of claim 38, wherein the step of providing aguide assembly further comprises providing a blunt tip tubular memberhaving a tubular member lumen within a tubular member body extendingfrom a proximal tubular member end to a distal tubular member as saidtubular member.
 43. The method of claim 38, wherein the step ofproviding a guide assembly further comprises providing a trocar having atrocar lumen within a trocar body extending from a proximal trocar endto a distal trocar end as said tubular member.
 44. The method of claim38, wherein the step of providing a guide assembly further comprisesproviding a guide sheath having a guide sheath lumen within a guidesheath body extending from a proximal guide sheath end to a distal guidesheath end as said tubular member.
 45. The method of claim 38, whereinthe guidewire fixation mechanism comprises a distal screw-in tip adaptedto be screwed into sacral bone.
 46. The method of claim 38, wherein theguidewire fixation mechanism comprises a distal sharpened tip adapted tobe pushed into sacral bone.
 47. The method of claim 38, furthercomprising: dilating the tissue surrounding the guidewire body;providing an enlarged diameter posterior tract sheath having a tractsheath lumen extending between proximal and distal posterior tractsheath ends; and inserting said posterior tract sheath through saidenlarged posterior tissue tract over said guidewire to position saidenlarged diameter posterior tract sheath distal end against theposterior sacrum.
 48. The method of claim 47, wherein the step ofdilating the tissue further comprises: providing a dilation ballooncatheter having a balloon in the deflated state; and expanding thedeflated balloon to an expanded state to dilate the presacral tissuebetween the posterior sacral surface and the dermal entry site.